Catalyst Design Based on Functionalized Phosphines with a Compact Coordination Center

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1. Research with Caged Phosphine SMAPThe procedure for the synthesis of Ph-SMAP, the parent compound for various SMAP derivatives, was improved. It was confirmed that Ph-SMAP is an excellent ligand for hydrosilylation and hydrgenation of ketones.SMAP was immobilized on silica gel surface. Silica-SMAP thus obtained showed very high ligand performance for the Rh-catalyzed hydrosilylation and hydrogenation of sterically demanding ketones.Furthermore, Silica-SMAP was successfully used for the development of Ir-catalyzed directed ortho borylation of functionalized arenes.SMAP derivatives bearing an alkanethiol pendant at the bridgehead silicon atom was prepared and used for the preparation of self-assembled monolayer on gold surface. Au-SMAP thus prepared showed remarkably high activity and turnover efficiency in the Rh-catalyzed dehydrogenative alcohol silylation.2. Research with Semihollow TrialkynylphosphinesTriethynylphosphine ligands with different end-cap groups were synthesized. Those with bulky end-caps showed unique coordination properties to form 1:1 metal-phosphine complexes selectively with various transition metal species. The semihollow-shaped triethynylphosphines showed extraordinally high accelerating effect in the Rh-catalyzed hydrosilylation of ketones. Furthermore, the semihollow triethynylphosphines were successfully used as ligands for gold-catalyzed alkyne cyclizations. In particular, the accelerating effect in the 6-exo-dig and 7-exo-dig cyclization was remarkable. In addition, this catalyst system enabled unprecedented cyclizations of internal alkyne derivatives.